The present disclosure relates to apparatus and methods for actuating rotatable members and, more specifically, for actuating rotatable aircraft control surfaces.
Many existing commercial and military aircraft include a pressurized fuselage, a wing assembly positioned toward a middle portion of the fuselage, and a tail assembly positioned aft of the wing assembly. The tail assembly typically includes horizontal control surfaces that provide pitch control, and vertical control surfaces that provide yaw control. The tail assembly may be mounted to an unpressurized empennage attached to an aft portion of the fuselage. Alternately, some aircraft are equipped with canard surfaces that are mounted on the fuselage at locations forward of the wing assembly and which provide the desired pitch stability and control. Regardless of the location of the control surface on the aircraft, many existing control surfaces (pitch and yaw) may be actuated by rotating a rotatable member (e.g. a drive shaft). Typically, the rotation of the rotatable member causes a corresponding deflection or rotation of the control surface, thereby providing the desired pitch or yaw control.
A side elevational view of a conventional actuator assembly 20 for actuating a rotatable control surface 22 is shown in FIG. 1. The actuator assembly 20 includes a longitudinally-extendible actuator 24 that is extendible in a first direction 26, and retractable in a second direction 28. The actuator 24 has a first end 30 pivotally coupled at a first point A to a first end 32 of a drive arm 34. A second end 36 of the drive arm 34 is non-pivotally (e.g. rigidly) coupled to a drive shaft 38 (shown in end view in FIG. 1) at a second point B. The drive shaft 38 is, in turn, coupled to the control surface 22.
As shown in FIG. 1, a second end 40 of the actuator 24 is pivotally coupled at a third point C to a first end 44 of a hangar link 42. A second end 46 of the hangar link 42 is pivotally coupled at a ground point G to a relatively stationary support 48 (e.g. an airframe). The actuator assembly 20 further includes a reaction link 50 having a first end 52 pivotally coupled to the second point B, and a second end 54 pivotally coupled to the third point C. Alternately, for applications that require increased torque, the drive arm 34 may extend beyond the second point B, and the reaction link 50xe2x80x2 may be pivotally coupled to the second end 36xe2x80x2 of the elongated drive arm 34xe2x80x2 at an alternate point Bxe2x80x2.
In operation, as the actuator 24 is extended in the first direction 26, a force is exerted on the drive arm 34 that, coupled with a corresponding force in the reaction link 50, causes a rotation of the drive shaft 38, thereby rotating the control surface 22 in a first rotational direction 52. Similarly, when the actuator 24 is retracted in the second direction 28, the combination of forces in the drive arm 34 and the reaction link 50 cause the drive shaft 38, and thus the control surface 22, to rotate in a second rotational direction 54. Because the second end 46 of the hangar link 42 is pivotally coupled at the ground point G, the third point C may translate in the first and second directions 26, 28 during actuation of the actuator 24. Thus, actuation loads provided by the actuator 24 are close-coupled to local structure through the reaction link 50, which is conventionally attached to the second point B, or to the alternate point Bxe2x80x2 that is co-linear with the first and second pivot points A and B. Similarly, torsional loads are reacted by the hangar link 42. The actuator assembly 20 shown in FIG. 1 is of a type commonly-known as a xe2x80x9cwalking beamxe2x80x9d kinematic linkage assembly.
Although desirable results have been achieved using the conventional actuator assembly 20, continued advances in aircraft technology are placing increased demands on such assemblies. For example, in some advanced aircraft configurations, particularly those being developed for trans-sonic and supersonic flight conditions, it may be desirable to provide relatively large canard surfaces for optimal pitch control, while at the same time reducing the size of the aircraft fuselage cross-section to minimize drag. These factors may tend to increase the load requirements on the actuator assembly, while at the same time increasing the demand for more effective utilization of space within the aircraft. Thus, there is an unmet need to provide actuator assemblies that more fully satisfy the competing demands being presented by continued advances in aircraft technology.
The present invention is directed to apparatus and methods for actuating rotatable members. Apparatus and methods in accordance with the present invention may advantageously decrease the amount of space occupied by such apparatus in comparison with the prior art. When used in aircraft, the apparatus and methods disclosed herein may therefore provide improved utilization of space within the aircraft.
In one embodiment, an assembly for actuating a rotatable member includes an extendible actuator having a first end and a second end, and a drive member having a first portion pivotally coupled to the second end, and a second portion non-pivotally coupled to the rotatable member. The second portion of the drive member is spaced apart from the first portion. The drive member further includes a third portion spaced apart from the first and second portions in a non-linear orientation. The assembly further includes a reaction link having an anchoring end pivotally coupled to the first end of the extendible actuator, and a driving end pivotally coupled to the third portion of the drive member.